I have Equallogic PS6000XV working along with XenServers. I have some volumes showing wrong free space counts. I get in-use warning but actually the drive has no data at all (free). How happens this error? Please find the attached screenshot and see the warning. The volume shows there actually free of data but equallogic wrongly notifies as if it's full.
This sounds like a case of the array not reclaiming unused disk space. If you move the xen vm's off this data store to another datastore the volume will still show used space even though its empty because the iSCSI file system can not get change blocks on the volume. If you delete the volume and recreate you will have your space back.